For example, in an electrophotographic image forming apparatus (hereinafter referred to as an “image forming apparatus”) such as a copying machine or a laser beam printer, an electrostatic image (electrostatic latent image) is formed by applying light corresponding to image data onto an electrophotographic photosensitive member (photosensitive member). Toner serving as developing agent is supplied from a developing device to the electrostatic image to develop the electrostatic image into a visible toner image. This toner image is transferred from the photosensitive member onto a recording medium, such as recording paper, by a transfer device, and is then fixed on the recording medium by a fixing device. Through the above procedure, a recorded image is obtained.
Various developing devices using a dry one-component developing method have been proposed. In an example of such a developing device, toner serving as one-component developing agent is stored in a developing container. The toner is born on a developing roller rotatably fixed in the developing container, and a toner layer of a uniform thickness is formed by a developing-agent regulating member. The developing roller bearing the toner layer is located close to or in contact with the photosensitive member and, for example, a developing bias voltage including an alternating-current component and a direct-current component is applied to the developing roller to generate a potential difference between the electrostatic image on the photosensitive member and a developing sleeve. The toner is thereby transferred onto the electrostatic image to develop the electrostatic image.
As a method for regulating the thickness of the toner layer formed on the developing roller, a so-called cantilevered method is disclosed in Japanese Patent Laid-Open No. 5-142933. In this method, an elastic regulation blade is used as a developing-agent regulating member, and is fixed to a developing container such as to contact with a developing-agent bearing member in a bent state. Since a pressure generated by bending the regulation blade is used as a regulation pressure for regulating the developing agent, a desired regulation pressure can be stably obtained even if mount positions of the developing-agent bearing member and the developing-agent regulating member vary.
Japanese Patent Laid-Open No. 9-211966 discloses a method in which a rigid body is used as a developing-agent regulating member and a spring member is provided between the developing-agent regulating member and a developing container. The developing-agent regulating member is pressed against a developing-agent bearing member from above by the spring member. Since a biasing pressure of the spring member is used as a regulation pressure for the developing agent, a desired regulation pressure can be stably obtained even if mount positions of the developing-agent bearing member and the developing-agent regulating member vary.
In recent years, the image forming apparatus has been required to have not only higher image quality but also smaller size, in particular, smaller thickness.
However, in the structure disclosed in Japanese Patent Laid-Open No. 5-142933, the regulation pressure for the developing agent is obtained by bending the elastic regulation blade. For this reason, as illustrated in FIG. 27, a space S1 where a regulation blade 23 is bent is needed to be formed between a fixing portion for fixing the regulation blade 23 to a developing container 22 and a regulation position 25 for the developing agent set on the developing-agent bearing member 24.
In the structure disclosed in Japanese Patent Laid-Open No. 9-211966, as illustrated in FIG. 28, a space S2 storing a developing-agent regulating member 28 formed by a rigid body and a spring member 29 is needed to be formed above a developing-agent bearing member 24 and between a developing container 26 and a regulation position 27 for the developing agent.